主题链接：
id=2513
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Colored Sticks
Description You are given a bunch of wooden sticks. Each endpoint of each stick is colored with some color. Is it possible to align the sticks in a straight line such that the colors of the endpoints that touch are of the same color? Input Input is a sequence of lines, each line contains two words, separated by spaces, giving the colors of the endpoints of one stick. A word is a sequence of lowercase letters no longer than 10 characters. There is no more than 250000 sticks. Output If the sticks can be aligned in the desired way, output a single line saying Possible, otherwise output Impossible. Sample Input blue red red violet cyan blue blue magenta magenta cyan Sample Output Possible Hint Huge input,scanf is recommended. Source |
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题目意思：
有n条木棒。每条木棒两端有两种颜色，求这些木棒是否能能在一起，使得前一个木棒的后端颜色和前一个木棒的前端颜色一样。
解题思路：
欧拉通路+字典树+并查集
注意是无向边。注意要推断连通性。直接用map映射会超时，自己写字典树。
代码：
//#include<CSpreadSheet.h>
#include<iostream>
#include<cmath>
#include<cstdio>
#include<sstream>
#include<cstdlib>
#include<string>
#include<string.h>
#include<cstring>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<ctime>
#include<bitset>
#include<cmath>
#define eps 1e-6
#define INF 0x3f3f3f3f
#define PI acos(-1.0)
#define ll __int64
#define LL long long
#define lson l,m,(rt<<1)
#define rson m+1,r,(rt<<1)|1
#define M 1000000007
//#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
#define Maxn 550000
int dei[Maxn],a[Maxn],cnt,la;
struct Node
{
struct Node * next[30];
int nu;
}node[Maxn*15],root;
int Insert(char *a)
{
Node * p=&root;
while(*a)
{
if(p->next[*a-'a'+1]==NULL)
{
node[++la].nu=0;
memset(node[la].next,NULL,sizeof(node[la].next));
p->next[*a-'a'+1]=&node[la];
}
p=p->next[*a-'a'+1];
a++;
}
if(!p->nu)
p->nu=++cnt;
return p->nu;
}
int Find(int x)
{
int temp=x;
while(x!=fa[x])
x=fa[x];
while(fa[temp]!=x)
{
int cur=fa[temp];
fa[temp]=x;
temp=cur;
}
return x;
}
void Unio(int a,int b)
{
a=Find(a),b=Find(b);
if(a!=b)
fa[a]=b;
}
int main()
{
memset(dei,0,sizeof(dei));
string a,b;
char sa[15],sb[15];
cnt=la=0;
for(int i=1;i<=Maxn-5000;i++)
fa[i]=i;
memset(root.next,NULL,sizeof(root.next));
root.nu=0;
while(~scanf("%s%s",sa+1,sb+1))
{
int a=Insert(sa+1);
int b=Insert(sb+1);
dei[a]++,dei[b]++;
Unio(a,b);
}
bool ans=true;
int nui=0,nuo=0,la=-1;
for(int i=1;i<=cnt;i++)
{
if(la==-1)
la=Find(i);
else if(la!=Find(i))
{
ans=false;
break;
}
if(dei[i]&1)
nui++;
}
if(!ans||nui>2||nui==1)
printf("Impossible\n");
else
printf("Possible\n");
//system("pause");
return 0;
}
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